Patent GB-830979-A (GB)
Title: Improvements in or relating to electrical adding circuits
IPC: G06F7/40
Filed: 1957-03-18
Abstract: 830,979. Digital electric calculating apparatus; counting-apparatus. GENERAL ELECTRIC CO. Ltd., and SMART, N. C. March 18, 1958 [March 18, 1957], No. 8827/57. Class 106 (1). An electrical adding and subtracting circuit comprises a binary counter having for each stage an output and an electromagnetic-relay controlled input whereby a number may be added in parallel to the number registered by the counter, the total registered by the counter being indicated by the states of the outputs. Binary counter.-The first pulse applied to a lead 7 energizes a relay A of the first binary stage 1 over its winding 21 so that on termination of the pulse, a relay B is energized over the contact A1, its contacts B1, B2 changing over to form a path for the second pulse at 7 to the second binary stage 2, the second pulse also serving to reset the first stage 1 by releasing firstly the relay A and then the relay B. The counter stages are decoupled by rectifiers such as 44. Contacts A3 when closed indicate that the associated binary stage is registering a "1." Subsequent stages 2, 3, &c., operate in a similar manner. The total count is indicated by the potentials applied over contacts A3, G3, &c., to leads 8, 9, &c., " 0 " and " 1 " being indicated by low and high potentials respectively. Addition.-To add in parallel to a number registered by the counter, leads 14, 15, &c., are energized or not according to the binary input digit to energize or not relays V, W, &c. Thus if stage 1 registers a " 1 " (i.e. the relays A and B are operated), then energization of the relay V to close its contacts V1 results in the relays A, B being reset, and a pulse being passed over the lead 26 to the next stage 2. If stage 2 was originally registering a "1," and the relay W has been energized, then a pulse over the lead 26 is applied over contacts W2, D3 to a winding 34 of a relay C which does not release as positive potential is also applied over contacts W1, D1. A positive pulse is however applied to the lead 27 to the next stage. The result of the addition is indicated by the potentials on the output leads 8, 9, &c. The device may be reset by disconnecting the power supply, by supplying further counting pulses to the lead 7, or by adding an appropriate amount over the leads 14, 15, &c. Subtraction.-A subtraction circuit (Fig. 3, not shown), which is basically similar to the addition circuit is described, the terminals 25 &c. being connected to positive instead of negative so that the complement of the number incident at the leads 14, 15, &c., is added to the number registered in the counter. If this operation results in a carry to the highest stage, i.e. the input number is smaller in magnitude than the numbers registered by the counter, a " 1 " is added into the lowest stage so that the counter indicates the required difference. If there is no such carry, i.e. the input number is greater in magnitude than the number registered by the counter the magnitude of the required difference, which is the complement of the number registered by the counter, is arranged to be indicated.